Facsimile recorders as contemplated by the present invention receive data from a transmitter and convert the signal to electrical impulses that are recorded on a web of electrolytic recording paper. Such devices feed the web of recording paper between a pair of opposing electrodes, one of which is fixed and the other of which sweeps across the paper. As electrical impulses occur across the electrodes during the sweep, the web of electrolytic paper which is disposed therebetween will discolor and marks will be made. A series of marks will form a line by line representation of the graphic information which is being transmitted.
The facsimile messages are sent at predetermined speeds or sweep rates in order to effectively utilize the transmission medium. Prior to the transmission of a message, these sweep rates are selected by an operator of the transmitting unit and generally are a function of the density of the information to be transmitted and the capacity of the communications link which will receive the information. Recorders which receive these transmissions function unattended and hence must be able to commence operation when a signal is received for starting and also operate at the sweep rate that is being utilized by the operator of the transmitting unit. Prior to sending the information, the operator of the transmitter will send a starting signal followed by a series of control phasing pulses which are transmitted once during each sweep of a line of the graphic information. Before graphic information is transmitted, these pulses are sent with no information between them and in this way, the equipment can be told the sweep rate that it must utilize in order to record the graphic information correctly.